ra_gif(1) convert RADIANCE picture to Compuserve GIF


ra_gif [ -b ][ -d ][ -c ncolors ][ -g gamma ][ -e +/-stops ][ -n sampfac ] input [ output ]


Ra_gif converts from RADIANCE to Compuserve GIF color-mapped, compressed image files. In the default mode, a RADIANCE picture is converted to a color-mapped GIF file of the same horizontal and vertical dimensions with 8-bits per pixel. The -b option converts the image to black and white. The -d option turns off dithering. The -c option allows fewer than 256 colors (and fewer than 8 bits per pixel). The -g option specifies the exponent used in gamma correction; the default value is 2.2. An exponent of 1.0 turns gamma correction off. The -e option specifies an exposure compensation in f-stops (powers of two). Only integer stops are allowed, for efficiency. The -n option specifies a sampling factor for neural network color quantization. This value should be between 1 and 80, where 1 takes the longest and produces the best results in small areas of the image. If no value is given, a faster median cut algorithm is used. If the output file is missing, the standard output is used.


Greg Ward
Paul Haeberli
David Rowley
Anthony Dekker provided the code for neural network color quantization